Automated control valves such as, for example, rotary control valves, are often used in process control plants or systems to control the flow of process fluids. A rotary control valve typically includes an actuator (e.g., a pneumatic actuator, an electric actuator, a hydraulic actuator, etc.) operatively coupled to a valve shaft extending from the rotary valve via a lever. The lever converts a rectilinear displacement of an actuator stem into a rotational displacement of the valve shaft. Thus, rotation of the lever causes the valve shaft and a flow control member (e.g., a disk, a ball, etc.) coupled to the valve shaft to rotate relative to a valve seat to allow fluid flow through the valve (e.g., an open position) or restrict fluid flow through the valve (e.g., a closed position). In operation, the actuator stem can move or tilt laterally relative to a longitudinal axis of the actuator housing to enable the lever to rotate. In the closed position, the actuator stem imparts a torque to the flow control member via the lever so that the flow control member sealingly engages the valve seat to prevent fluid flow through the valve.
A rotary valve often employs a diaphragm and spring actuator. The diaphragm moves between a first position at which the springs are in an initial or preloaded compressed state (e.g., when the valve is in an open position) and a second position at which the springs are in a fully compressed state (e.g., when the valve is in a closed position). The actuator is configured to allow the springs to translate or shift within a housing of the actuator due to inherent side load forces generated by the springs when the springs are in the compressed state and/or due to the actuator stem moving or tilting relative to the longitudinal axis when the rotating the lever. However, such movement or shifting of the springs may cause a diaphragm plate to engage an inner surface of the actuator housing, which creates friction and/or can crimp, deform or otherwise damage the diaphragm and reduce the effective diaphragm area. Reducing an effective diaphragm area of the diaphragm can reduce the net amount of torque provided by the actuator to the flow control member when the flow control member engages the valve seat, thereby reducing the performance of the fluid control valve.